In this analogy, the choice that the pigeons have in picking up the grain (selectivity) and the energy they spend in the process of obtaining grains (actively) are the vital features. The tissue metabolism can influence the extent of vasodilatation and thus its own perfusion. This is known as auto-regulation of blood supply. Similarly, the specific kind of tissue has affinity for specific nutrient and other substances. For example, the calcium gets deposited normally in bones, but not in the mucous membranes. Similarly, vitamin B-12 is stored in liver and not in other tissues. | In this analogy, the choice that the pigeons have in picking up the grain (selectivity) and the energy they spend in the process of obtaining grains (actively) are the vital features. The tissue metabolism can influence the extent of vasodilatation and thus its own perfusion. This is known as auto-regulation of blood supply. Similarly, the specific kind of tissue has affinity for specific nutrient and other substances. For example, the calcium gets deposited normally in bones, but not in the mucous membranes. Similarly, vitamin B-12 is stored in liver and not in other tissues. |